1. Field of the Invention
The present invention relates to an area detection apparatus in which a reference image having a predetermined pattern is prepared beforehand, and an area having the same pattern as the reference image is detected from an inputted search image.
2. Description of the Related Art
It is desired to develop robots (including motor vehicles, unmanned motor vehicles and autonomous locomotion robots) for automatically conveying meals, washing and the like in medical and washing facilities such as hospitals or the like. In addition, it is desired to develop motor vehicles also in office buildings, inside rooms of schools, factories, etc., and in roads and the like. For environment measurement apparatuses needed in order that such motor vehicles travel on an autonomous basis, technology of detecting from a camera image a landmark within a traveling environment is important.
As a method of detecting from images a figure having a certain distinctive feature, for example, a landmark or the like, hitherto, there is applied a template matching scheme according to a correlation operation among images. According to such a template matching scheme, a landmark to be detected is set up beforehand in the form of a template image (a reference image), and a correlation operation is performed between an image to be searched and the template image, so that a high correlation area is detected.
An image of a landmark in a traveling environment is not constant in a brightness owing to a variation of a photographic condition, and thus there is a need to perform a proper detection in such a condition that luminance of images is greatly varied. In the correlation operation among images, however, a variation of luminance of images involves a great variation of a correlation value, and thus it is difficult to properly detect the landmark. In order to solve this problem, it is effective to adopt a method of applying a normalized correlation operation. However, the normalized correlation operation involves an increment of an amount of operations. Further, there is proposed a three-level broad-edge matching method (H. Okuda, et al. "Three-level Broad-Edge Matching based Real-time Tracking Vision", Collected Papers, 13th Academic Lecture Meeting, Robotics Society of Japan, pp. 321-322, 1995)(K. Sumi, et al. "Three-level Broad-Edge Matching based Real-time Robot Vision", Proc. International Conference Robotics and Automation, pp. 1416-1422, 1995).